Method for hydroforming a container from a preform

ABSTRACT

Assembly ( 30 ) of a preform ( 32 ) and a station ( 34 ) for hydroforming a container from the preform, wherein:
         the preform has a neck ( 44 ) extending along an axial direction (D), the neck comprising a support ring ( 46 ), and a finish ( 48 ),   the station comprises a mold ( 36 ) in which the preform is placed, the support ring being in contact with a support surface ( 56 ) of the mold,   the station comprises an injection nozzle that is movable along the axial direction with respect to the mold from a retracted position to an intermediate position, wherein a contact is established between a first contact surface ( 72 ) of the nozzle and the finish, and further to an injection position, wherein a second contact surface ( 74 ) of the nozzle abuts on an abutment surface ( 76 ) and the neck is axially compressed between the support surface and the first contact surface, the first contact surface being less deformable than the neck in the axial direction, and   the station is adapted for injecting a liquid from the nozzle into the preform when the nozzle is in the injection position, and the abutment surface is fixed along the axial direction with respect to the mold at least during the injection.

TECHNICAL FIELD OF THE INVENTION

The invention relates to the field known as hydroforming, of formingcontainers from preforms using a liquid to deform the preforms and fillthe obtained containers with said liquid.

The invention relates to an assembly of the preform and a station forhydroforming the preform.

The invention also relates to a method for forming a container from apreform, by injecting a liquid in said preform using an injectionnozzle.

In the application, “liquid” has a physical meaning. It designates anysubstantially incompressible medium able to flow. The liquid can have alow viscosity (like water or alcohol), a medium viscosity (like eatableoil or soup), or a high viscosity (like yoghurt or creamy product). Theliquid can be homogeneous or not homogeneous (including fruit pulp orbits of foodstuff). It is not limited to foodstuff. The liquid may befor example water, or other beverages, body care products, home andgarden care products, medical fluids, fuels, operating fluids, and thelike.

BACKGROUND

In the technical field of forming containers, hygiene is a veryimportant issue in order to prevent any risk of contamination of thecontent of the containers, for example bottles with products intended tobe ingested by consumers or applied on their skin. Consequently,preventing the contamination of any parts of the containers, of thehydroforming station, and of the liquid filling the containers is afundamental issue.

As shown in FIG. 1, a typical preform 1 has a neck 3 extending along anaxial direction D, which is generally vertical. The neck comprises asupport ring 5 protruding radially, and a finish 7 axially opposed tothe support ring.

A known type of station, such as the one shown in FIG. 1, comprises amold 9 in which the preform 1 is placed, the support ring 5 having afirst contact surface 11 in contact with a support surface 13 of themold, the neck protruding out of the mold.

The station also comprises an injection nozzle 15 that is movable alongthe axial direction D with respect to the mold 9 from a retractedposition (FIG. 1), wherein the nozzle is away from the neck 3, to a workposition wherein the neck is received in a housing 17 defined by theinjection nozzle. The housing 17 is in fluidic communication with theinterior of the preform 1 and with a source 19 of the liquid to beinjected in the preform. It is used for forming a container having theshape of the mold cavity. The injected liquid urges the preform 1 andexpands it against the mold cavity. In its work position, the nozzle 15abuts on an upper surface 21 of the mold 9. A drawback of such a formingstation is that the injected liquid may contaminate the outside lateralscrew surface of the neck.

As described in document WO-A-2013/096609, especially in its paragraph[0041] and FIG. 4, the injection nozzle may include a seal 71 arrangedto lie on the finish of the preform in order to prevent any leak ofliquid outside of the neck during the injection of the liquid into thepreform and thus to prevent contamination of the external wall of theneck by the injected liquid.

A seal is typically a ring made of a compressible material that issofter than a surface of the nozzle on which the seal is fixed andsofter than the neck when the seal is pressed against the finish. Forexample, such a seal is made of elastomeric material or silicone.

In order to achieve a high production rate of the hydroforming station,the nozzle is moved back and forth at high frequency, such as 1 Hz, fromthe retracted position to the work position. As the nozzle is a ratherheavy part, of typically 50 kg, large efforts, in the range of 3000 N,are applied on it in order to achieve these quick movements. To resistsuch a large axial force, the moving nozzle applies against the mold.

When the nozzle is applied upon the mold, the seal is pressed againstthe finish in order to provide a liquid tight sealing between the nozzleoutlet and the inner volume of the preform. However, the frequency ofthe up and down movements may eventually damage the seal in such a waythat leaks occur. Also, bits of the seal may ultimately contaminate theliquid injected in the preform. Furthermore, with such production rates,the seal has a short life duration and must be regularly replaced.During replacement, the station is idle, which reduces the productionrate.

One of the aims of the invention is to provide an assembly forhydroforming a container that eliminates or at least reduces the leakproblems, while remaining economical and enabling a high productionoutput.

SUMMARY OF THE INVENTION

To this end, the invention relates to an assembly of a preform and astation for hydroforming a container from the preform, wherein:

-   -   the preform has a neck extending along an axial direction, the        neck comprising a support ring protruding radially, and a finish        axially opposed to the support ring,    -   the station comprises a mold in which the preform is placed, the        support ring being in contact with a support surface of the        mold,    -   the station comprises an injection nozzle that is movable along        the axial direction with respect to the mold from a retracted        position, wherein the nozzle is away from the neck, to an        intermediate position, wherein a contact is established between        a first contact surface of the nozzle and the finish, and        further to an injection position, wherein a second contact        surface of the nozzle abuts on an abutment surface and the neck        is axially compressed between the support surface and the first        contact surface, the first contact surface being less deformable        than the neck in the axial direction, and    -   the station is adapted for injecting a liquid from the nozzle        into the preform when the nozzle is in the injection position,        and the abutment surface is fixed along the axial direction with        respect to the mold at least during the injection.

With the assembly according to the invention, there is no need for asealing ring between the finish of the preform and the injection nozzle.

However, thanks to the second contact surface of the nozzle abutting onan abutment surface and the neck being axially compressed between thesupport surface of the mold and the first contact surface of the nozzle,with the abutment surface being substantially fixed along the axialdirection with respect to the mold at least during the injection, theneck is compressed during the injection in a controlled way, so as toprevent leaks towards the external wall of the neck.

As the nozzle movement towards its injection position is stopped by thesecond contact surface of the nozzle abutting on the abutment surface,the actuators of the nozzle may be of a traditional type, like apneumatic piston or the like, thus reducing the cost of the hydroformingstation.

The axial deformation of the neck provides the desired contact pressureon the finish. That pressure is determined in order to obtain a reliableliquid tightness on the finish. In its life time, the neck of thecontainer will support only once such an axial deformation. This is verydifferent from the seal ring 71 described in WO2013/096609, wherein thesame seal ring has to endure a strong compression deformation for eachmanufactured container. Such a seal ring 71 has to endure millions ofcompression cycles during its life time. In the invention, as thematerial compressed and deformed to provide the sealing pressure is notincluded in the forming station, the forming station can have first andsecond contact surfaces robust enough to prevent wear and tear.

In other embodiments, the assembly comprises one or several of thefollowing features, taken in isolation or any feasible combination:

-   -   the nozzle in the injection position is closer to the mold than        in the intermediate position, and the axial distance from the        intermediate position to the injection position is greater than        0.1 mm;    -   the neck has an initial axial extension when the nozzle is in        the retracted position, and has a reduced axial extension when        the nozzle is in the injection position, and    -   the location of the abutment surface along the axial direction,        and the axial distance between the first contact surface and the        second contact surface are adapted so that the difference        between the initial axial extension and the reduced axial        extension ranges from 0.2 mm to 0.4 mm, and is preferably around        0.3 mm; and    -   the nozzle comprises at least an end part made of metal and        defining the first contact surface.

Thanks to the metallic contact between the nozzle and the finish, thesealingness of that contact is very stable along the successive formedcontainers. Additionally the sealing surface is easy to clean.

According to another optional feature, the end part is integral andfurther defines the second contact surface. This provides a very stablesealing force on the finish, independent from vibration or shocks withinthe station.

According to another optional feature, the end part comprises a distalpart defining the second contact surface, a proximal part, and alaminated shim located between the distal part and the proximal partalong the axial direction, the laminated shim being suitable foradjusting the axial distance between the first contact surface and thesecond contact surface by varying the axial dimension of the shim. Thisprovides both a very stable and an adjustable sealing force.

According to another optional feature, the abutment surface is definedby the mold. This allows high throughput for the forming station,because the force moving the injection nozzle can be increased in orderto reduce the cycle time.

According to another optional feature, the abutment surface is definedby the support ring, the abutment surface being axially opposed to acontact surface of the support ring, the contact surface being incontact with the support surface of the mold. This provides a betterstability of the preform within the mold during the injection.

According to another optional feature, the assembly further comprises aninjection head including a head body having a fixed axial position withrespect to the mold at least while the injection nozzle is in theinjection position, the injection nozzle being axially movable withrespect to the head body. This allows free space around the neck of thepreform which can be used for another function, such as implementing asensor or the like.

According to another optional feature, the abutment surface is definedby a stop element rigidly fixed to the head body at least while theinjection nozzle is in the injection position and axially adjustablewith respect to the head body so as to adapt the assembly to differentinitial axial extensions of the neck. This allows both a free spacearound the preform neck and an adjustable station for different neckheights.

According to another optional feature, the first contact surface of thenozzle is perpendicular to the axial direction. This minimizes thedeformation of the neck during the forming of the container.

According to another optional feature, the second contact surface of thenozzle laterally extends from the neck or has a “C” shape around theneck, so as to enable an access to the neck from a free side of the neckwhile the injection nozzle is in the intermediate position. Said accessfrom a free side of the neck can be used for example by a gripper. Thisreduces the length and duration of the reciprocating movement of theinjection nozzle, and increases the throughput of the forming station.

The invention also relates to a method for hydroforming a container froma preform having a neck extending along an axial direction, the neckcomprising a support ring protruding radially, and a finish axiallyopposed to the support ring, the method comprising the steps of:

-   -   placing the preform in a mold so that the support ring is in        contact with a support surface of the mold,    -   moving an injection nozzle along the axial direction with        respect to the mold from a retracted position wherein the nozzle        is away from the neck, to an intermediate position wherein a        contact is established between a first contact surface of the        nozzle and the finish,    -   further moving the nozzle from the intermediate position to an        injection position, wherein a second contact surface of the        nozzle abuts on an abutment surface and the neck is axially        compressed between the support surface and the first contact        surface, the first contact surface being less deformable than        the neck in the axial direction, and    -   injecting a liquid from the nozzle into the preform, the nozzle        being in the injection position, the abutment surface being        fixed along the axial direction with respect to the mold at        least during said injecting.

In other embodiments, the method may comprise the following features:

-   -   the neck has an initial axial extension when the nozzle is in        the retracted position, and has a reduced axial extension when        the nozzle is in the injection position, the location of the        abutment surface along the axial direction, and the axial        distance between the first contact surface and the second        contact surface being adapted so that the difference between the        initial axial extension and the reduced axial extension is        greater than 0.1 mm, preferably ranges from 0.2 mm to 0.4 mm,        and is more preferably around 0.3 mm, and/or    -   the axial distance along which the injection nozzle is moved        during said moving of the nozzle from the intermediate position        to the injection position is greater than 0.1 mm, preferably        ranges from 0.2 mm to 0.4 mm, and is more preferably around 0.3        mm.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects and advantages of the invention will appear upon readingthe following description, given by way of example and made in referenceto the appended drawings, wherein:

FIG. 1 is a diagrammatical view of a prior art hydroforming station,

FIG. 2 is a diagrammatical axial cross-section view of an assemblyaccording to a first embodiment of the invention,

FIG. 3 is a diagrammatical axial cross-section view of an assemblyaccording to a second embodiment of the invention,

FIG. 4 is diagrammatical axial cross-section view of an assemblyaccording to a third embodiment of the invention,

FIG. 5 is a diagrammatical axial cross-section view of an assemblyaccording to a fourth embodiment of the invention,

FIG. 6 is a diagrammatical axial cross-section view of a variant of thefirst and of the second embodiments of the invention, and

FIG. 7 is a transversal cross-section view according to plan VI-VI ofFIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, the terms “upper” and “lower” are definedrelative to an axial direction D, which corresponds to the axis of acontainer to be produced. For example the axial direction D extendssubstantially vertically when the container is placed on its bottom.

Referring to FIG. 2, there is described an assembly 30 of a preform 32and a station 34 for hydroforming a container (not shown) from thepreform.

The assembly 30 is substantially symmetrical around the axial directionD.

The station 34 comprises a mold 36 for receiving the preform 32, and aninjection head 38 suitable for injecting a liquid into the preform inorder to shape the preform into the container and advantageously also inorder to fill in the container.

The preform 32 and the preform 1 shown in FIG. 1 may be similar. Thepreform 32 comprises a hollow body 40 defining an inner volume 42, and aneck 44 extending along the axial direction D. The preform 32 may have ashape similar to that of a test tube being closed at a lower end alongthe axial direction D and having the neck 44 at an upper end.

The preform 32 is made of any suitable plastic materials, such aspolyesters, such as polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyethylene imine (PEI), polytrimethyleneterephthalate (PTT), polylactic acid (PLA), polyethylene furanoate(PEF), or polyolefins, such as polyethylene low density (LDPE) or highdensity (HDPE), polypropylene (PP), or styrene based materials such aspolystyrene (PS), acrylonitrile butadiene styrene (ABS) or otherpolymers, such as polyvinyl chloride (PVC).

The preform 32 is generally produced according to an injection moldingprocess and molded at a site different from the site where the station34 is located.

The hollow body 40 is for example cylindrical and extends axially.

The neck 44 generally has the final shape of the neck of the containerto be produced. The neck 44 comprises a radially protruding support ring46, and a finish 48 axially opposed to the support ring and defining anopening 50 of the preform 32 along the axial direction D.

A lower surface of the support ring 46 defines a first contact surface52 of the neck 44 with the station 38.

The first contact surface 52 is for example substantially perpendicularto the axial direction D and has an annular shape surrounding the neck44.

The mold 36 for receiving the preform 32 defines a molding cavity 54having the shape of the container to be produced. The mold 36 alsodefines a support surface 56 adapted to support the first contactsurface 52 of the support ring 46. When the preform 32 is placed in themold 36, the neck 44 protrudes from the mold 36 and the first contactsurface 52 rests on the upper surface of the mold, said upper surfacedefining the support surface 56.

The mold 36 comprises for example at least two parts (not shown) movablerelative to each other, between an open position, wherein the preform 32can be placed in the mold and the formed container can be retrieved fromthe mold, wherein the two parts define together the molding cavity 54,and a closed position when the preform is placed in the mold, whereinsaid molding cavity is closed in a liquid tight manner. The two partsare for example hinged together and are movable in rotation relative toeach other around an axis substantially parallel to the axial directionD.

The injection head 38 comprises a head body 58 and an injection nozzle60.

The head body 58 is for example in a fixed axial position with respectto the mold 36. By “fixed” it is meant that the head body 58 isimmovable relative to the mold 36 along the axial direction D.

The nozzle 60 comprises an end part 62 defining an outlet 64 for theliquid to be injected into the preform, and a nozzle body 66 attached tothe end part, the nozzle body 66 and the end part 62 defining aninternal chamber 68 for the liquid to be injected into the preform 32.The nozzle 60 also comprises a control rod 70 extending axially withinthe internal chamber 68 and movable axially with respect to the nozzlebody between a closing position, in which an extremity of the controlrod 70 is in liquid tight contact with the end part 62 in order to closethe outlet 64, and an opening position, in which the control rod 70 isaway from the end part 62 in order to let the liquid flow outside of theinternal chamber 68.

The injection nozzle 60 may further comprise a stretch rod 71 in thecentre of the control rod 70. The stretch rod 71 is known per se andwill not be described here.

The nozzle 60 is movable along the axial direction D with respect to themold 36 from a retracted position, wherein the nozzle is away from theneck 44, to an intermediate position, wherein a contact is establishedbetween a first contact surface 72 of the nozzle and the finish 48 ofthe neck 44, and further to an injection position (shown in FIG. 2),wherein a second contact surface 74 of the nozzle abuts on an abutmentsurface 76 and the neck 44 is axially compressed between the supportsurface 56 of the mold 36 and the first contact surface 72.

The nozzle 60 is closer to the mold 36 in the injection position than inthe intermediate position along the axial direction D. The axialdistance between the intermediate position and the injection position isfor example greater than 0.1 mm.

The retracted position of the nozzle 60 can be obtained from FIG. 2 bymoving the nozzle up along the axial direction D with respect to themold 36, so that the end part 62 is away from the mold and the neck 44to allow the mold to be opened.

The intermediate position can be obtained from FIG. 2 by moving thenozzle 60 up along the axial direction D with respect to the mold 36, sothat the end part 62 is away from both the mold, but still in contactwith the neck 44 which expands axially between the support surface 56 ofthe mold and the first contact surface 72. In the intermediate position,the neck 44 is only in contact with the first surface 72 and is notcompressed.

The end part 62 is integral and for example made of metal. The end part62 is for example screwed into the nozzle body 66 along the axialdirection D.

In the injection position, the end part 62 surrounds the neck 44 aroundthe axial direction D. A space 77 is provided between the neck 44 andthe interior of the end part 62. Said space may be used to host a sensorfor example, or may be radially close enough from the thread extremityto limit the radial deformation of the neck 44 when a liquid under highpressure is injected into the preform 1.

The first contact surface 72 is for example formed by an inner shoulderof the end part 62. The first contact surface 72 is advantageouslysubstantially perpendicular to the axial direction D. Therefore theaxial movement of the injection nozzle will not provoke radial orlateral deformation of the neck 44.

The first contact surface 72 is less deformable than the neck 44 in theaxial direction, meaning that the first contact surface 72 is notcompressed in the axial direction when said first contact surface isapplied against the finish 48 of the neck 44. The first contact surface72 compresses no seal that would be more deformable than the neck 44along the axial direction D.

The second contact surface 74 is for example defined by a lower annularface of the end part 62, advantageously perpendicular to the axialdirection D. The internal diameter ID of the second contact surface 74is large enough so that the end part 62 does not abut against thesupport ring 46.

The abutment surface 76 is for example defined by an upper face of themold 36, and is advantageously perpendicular to the axial direction D.

The neck 44 has an initial axial extension E1 when the nozzle 60 is inthe retracted position, and has a reduced axial extension E2 when thenozzle is in the injection position. By “axial extension” it is meantthe length of the neck 44 along the axial direction D.

The location of the abutment surface 76 along the axial direction D, andthe axial distance E3 between the first contact surface 72 and thesecond contact surface 74 are adapted so that the difference between theinitial axial extension E1 and the reduced axial extension E2 is greaterthan 0.1 mm or ranges from 0.2 mm to 0.4 mm, and is preferably around0.3 mm. This means that the length of the neck 44 in the axial directionD is reduced by 0.2 mm to 0.4 mm when the nozzle 60 is applied againstthe neck in the injection position.

The nozzle body 66 is for example made of a hollow cylinder. The nozzlebody 66 is axially movable with respect to the head body 58. Forexample, the nozzle body 66 is axially movable within the head body 58and displaced by a pneumatic system (not shown).

The internal chamber 68 is in fluidic communication with a source (notshow) of the liquid to be injected into the preform 32.

The liquid to be injected in the preform 32 by the station 34 is forexample the liquid that is intended to be in the container when thelatter is used by an end user (not shown).

A method for hydroforming a container from the preform 32 using thestation 34 (FIG. 2) will now be described.

First the preform 32 is placed in the mold 36. To do so, the mold 36 ismoved to its open position, the preform 32 is put in the mold, and themold is moved back to its closed position.

In any case, the first contact surface 52 of the support ring 46 lies onthe support surface 56 of the mold 36. The neck 44 is outside of thecavity 54.

Then the injection nozzle 60 is moved down along the axial direction Dwith respect to the head body 58 from the retracted position to theintermediate position. A contact is established between the firstcontact surface 72 of the end part 62 and the finish 48 of the neck 44.

At this point, the second contact surface 74 is not yet in contact withthe abutment surface 76 of the mold 36. The neck 44 has its initialaxial extension E1. The axial distance between the second contactsurface 74 and the abutment surface 76 is equal to E1 minus E2.

The nozzle 60 is further moved down axially until the second contactsurface 74 of the end part 62 abuts against the abutment surface 76. Theabutment surface 76 being fixed with respect to the mold 36, this stopsthe nozzle 60 in its injection position represented in FIG. 2.

While the nozzle 60 moves from its intermediate position to itsinjection position, the neck 44 is axially compressed progressivelybetween the support surface 56 of the mold 36 and the first contactsurface 72 of the end part 62. When the nozzle 60 reaches the injectionposition, the axial extension of the neck 44 is E2. In the injectionposition, the reduction of the axial extension of the neck 44 is equalto E1 minus E2.

The control rod 70 is then moved up in order to let the liquid flow fromthe internal chamber 68 of the nozzle 60 into the inner volume 42 of thepreform 32. The liquid urges the hollow body 40 against the walls of themolding cavity 54. The liquid shapes the preform 32 into the container(not represented). Advantageously, the liquid is also the liquid thatfills the container. In other words, the liquid will be contained in thecontainer and is intended to be used by an end user (not represented).

During the injection of the liquid into the preform 32, the finish 48presses against the first contact surface 72, which prevents the liquidfrom flowing outwardly between the finish 48 and the first contactsurface 72 and in the space between the neck and the interior of the endpart 62.

After injection, the control rod 70 is again pressed against the endpart 62 in order to seal the internal chamber 68.

The nozzle 60 is moved up axially back to its retracted position.

The neck 44 is not any more axially compressed and expands along theaxial direction D, for example until its axial extension is equal to theinitial axial extension E1.

The end part 62, having a fixed axial extension E3, is adapted toprovide the preform 32 with a given reduced axial extension E2.

If another kind of preform 32 is to be used, with a different initialaxial extension E1, the end part 62 may be replaced by another end parthaving a different axial extension E3 between the first contact surface72 and the second contact surface 74. In other words, due to its axialextension E3, the end part 62 is adapted to a given neck 44 having agiven initial axial extension E1, and requesting a desired compressionE1-E2 to act as a seal.

Thanks to the above mentioned features, the assembly 30 eliminates or atleast greatly reduces the leak problems, while remaining economical andenabling a high production output. Furthermore, the pressure applied onthe neck 44 by the nozzle 60 is precisely controlled, which reduces therisk of damaging the neck during the injection.

According to a second embodiment of the invention, an assembly 130 willnow be described in reference to FIG. 3.

The assembly 130 is analogous to the assembly 30 shown in FIG. 2. Theelements that are similar have the same numeral references and will notbe described again. Only the differences will be described in detailhereafter.

The injection nozzle 60 of the assembly 130 comprises an end part 162which differs from the end part 62 shown in FIG. 2.

The end part 162 includes a distal part 164 defining the second contactsurface 74, a proximal part 166, and a laminated shim 168 interposedbetween the distal part and the proximal part along the axial directionD.

For example the distal part 164 is screwed on the proximal part 166along the axial direction D.

For example a lower surface of the proximal part 166 defines the firstcontact surface 72.

The laminated shim 168 is for example located axially between a fourthcontact surface 170 of the distal part 164 and the first contact surface72. Such a laminated shim 168 is made of several layers of material andits extension or length in the axial direction D is adjustable byremoving one or more layers of the laminated shim. The layers are forexample peelable layers.

The fourth contact surface 170 if advantageously substantiallyperpendicular to the axial direction D.

The laminated shim 168 is adapted for adjusting the axial distance E3between the first contact surface 72 and the third contact 74 surface byvarying an extension E4 of the shim 168 along the axial direction D.

The assembly 130 is used in the same manner as the assembly 30, exceptthat the end part 162 does not have to be replaced by another end partin case another preform 32 with a different neck 44 has to be shaped.

By modifying the axial extension E4 of the laminated shim 168, it ispossible to change the axial distance E3 of the end part 162, whereasthe end part 62 has a fixed axial distance E3.

According to a third embodiment of the invention, an assembly 230 willnow be described in reference to FIG. 4.

The assembly 230 is analogous to the assembly 30 shown in FIG. 2. Theelements that are similar have the same numeral references and will notbe described again. Only the differences will be described in detailhereafter.

In the assembly 230, the abutment surface is not defined by the mold 36.

The head body 58 comprises a stop element 258 defining a stop whichdefines an abutment surface 276.

For example, the abutment surface 276 is defined by an upper face of alower part of the stop element 258 along the axial direction D.

The stop element 258 is for example rigidly fixed to the head body 58 atleast during the injection and advantageously axially adjustable withrespect to the head body 58 so as to make the assembly 230 cope withdifferent initial axial extensions E1 of the neck 44.

According to a fourth embodiment of the invention, an assembly 330 willnow be described in reference to FIG. 5.

The assembly 330 is analogous to the assembly 30 shown in FIG. 2. Theelements that are similar have the same numeral references and will notbe described again. Only the differences will be described in detailhereafter.

In the assembly 330, the end part 62 is adapted to abut against an upperface of the support ring 46. In other words, the support ring 46 definesan abutment surface 376.

The abutment surface 376 is opposed to the first contact surface 52 ofthe support ring 46 along the axial direction D.

The internal diameter ID of the second contact surface 74 is smallerthan the external diameter of the support ring 46.

The lower part of the end part 62 is advantageously truncated along theaxial direction D with a narrowing radial dimension towards the secondcontact surface 74.

In this embodiment, the support ring 46 being somewhat incompressibleaxially, its upper surface manages to act as an abutment surface for theend part 62.

A variant illustrated in FIGS. 6 and 7 defers from the first and secondembodiments by the shape of the contact between the injection nozzle 60and the mold 36. The end part 62 of the first embodiment or the distalpart 164 of the second embodiment are replaced by a side part 400providing a second surface 402 which is not annular. A pair of grippers410, that are generally not included in the forming station shown inFIG. 6, can access around the neck 44 from a free side of the neck. Thegrippers 410 are connected to the neck 44 at an axial position locatedbetween the support ring 46 and a holding ring 47. As illustrated inFIG. 7, the second contact surface 402 is limited to the space left freeby the grippers 410 connected with the neck 44.

Such a variant has the same advantages as the first and the secondembodiments, providing a robust direct stop of the injection nozzle 60against the mold 36, together with a reliable sealing on the finish 48and a robust and easy to clean contact surfaces. The variant provides anadditional advantage. It allows a reduction of the length and theduration of the axial movement requested for the injection nozzle 60.Said axial movement is indicated by the arrow 420. This reduces thetransition step of the forming process and allows higher throughputs ofthe forming station.

The above assemblies and methods have been described for a mold 36 thatis placed under the nozzle 60. However, the assembly and methods arealso suitable for a machine wherein the mold is placed above the nozzle,simply by interverting the terms “up” and “down” used above.

The assemblies and methods can also be adapted for a non vertical axialdirection D.

The invention claimed is:
 1. An assembly of a preform and a station forhydroforming a container from the preform, wherein: the preform has aneck extending along an axial direction, the neck comprising a supportring protruding radially, and a finish axially opposed to the supportring, the station comprises a mold in which the preform is placed, thesupport ring being in contact with a support surface of the mold, thestation comprises an injection nozzle that is movable along the axialdirection with respect to the mold from a retracted position, whereinthe nozzle is away from the neck, to an intermediate position, wherein acontact is established between a first contact surface of the nozzle andthe finish, and further to an injection position, wherein a secondcontact surface of the nozzle abuts on an abutment surface and the neckis axially compressed between the support surface and the first contactsurface, the first contact surface being less deformable than the neckin the axial direction, and the station is adapted for injecting aliquid from the nozzle into the preform when the nozzle is in theinjection position, and the abutment surface is fixed along the axialdirection with respect to the mold at least during the injection.
 2. Theassembly according to claim 1, wherein an axial distance from theintermediate position to the injection position is greater than 0.1 mm.3. The assembly according claim 1, wherein: the neck has an initialaxial extension when the nozzle is in the injection position, and thelocation of the abutment surface along the axial direction, and theaxial distance between the first contact surface and the second contactsurface are adapted so that the difference between the initial axialextension and the reduced axial extension rages from 0.2 mm to 0.4 mm.4. The assembly according to claim 1, wherein the nozzle comprises atleast an end part made of metal and defining the first contact surface.5. The assembly according to claim 4, wherein the end part is integraland further defines the second contact surface.
 6. The assemblyaccording the claim 4, wherein the end part comprises a distal partdefining the second contact surface, a proximal part, and a laminatedshim located between the distal part and the proximal part along theaxial direction, the laminated shim being suitable for adjusting theaxial distance between the first contact surface and the second contactsurface by varying the axial dimension of the shim.
 7. The assemblyaccording to claim 1, wherein the abutment surface is defined by themold.
 8. The assembly according to claim 1, wherein the abutment surfaceis defined by the support ring, the abutment surface being axiallyopposed to a contact surface of the support ring, the contact surfacebeing in contact with the support surface of the mold.
 9. The assemblyaccording to claim 1, further comprising an injection head including ahead body having a fixed axial position with respect to the mold atleast while the injection nozzle is in the injection position, theinjection nozzle being axially movable with respect to the head body.10. The assembly according to claim 9, wherein the abutment surface isdefined by a stop in the head body.
 11. The assembly according to claim9, wherein the abutment surface is defined by a stop element rigidlyfixed to the head body at least while the injection nozzle is in theinjection position and axially adjustable with respect to the head bodyso as to adapt the assembly to different initial axial extensions of theneck.
 12. The assembly according to claim 1, wherein the first contactsurface of the nozzle is perpendicular to the axial direction.
 13. Theassembly according to claim 1, wherein the second contact surface of thenozzle laterally extends from the neck or has a “C” shape around theneck, so as to enable an access to the neck from the free side of theneck while the injection nozzle is in the intermediate position.
 14. Theassembly according to claim 3, wherein the location of the abutmentsurface along the axial direction, and the axial distance between thefirst contact surface and the second contact surface are adapted so thatthe difference between the initial axial extension and the reduced axialextension is around 0.3 mm.